Unwrapping turns out really bard
So you don't want the top and the back to be disconnected from the front, right?

In that case, clear the seams from these two edges I painted blue:



You can do so by doing in Edit mode: Right click + Clear Seam. Then, unwrap the UVs again.

Notice how this model looks if I mark the top edges as Seam:



And notice how it looks by clearing the seam:



When you mark a seam you are telling Blender it's OK to disconnect that part of your object from the rest, so only mark them in places that you don't want connected on the resulting UV mapping.